1. Field of the Invention
The present invention relates to a method of increasing the sensitivity of a thermopile consisting of a plurality of thermocouples connected in series and use for the detection of temperature.
2. Description of the Prior Art
A thermopile, which comprises a heat sensitive portion which is sensitive to heat irradiated from an object to be measured and a standard portion which is maintained at a standard temperature such as room temperature and the like, produces detecting signals resulting from Seebeck's effect owing to temperature differences between the above described two portions. However, when temperatures are measured by means of said thermopile, although they can be accurately measured if the temperature of an object to be measured is sufficiently higher or lower than the standard temperature such as a room temperature, and the like (hereinafter referred to as merely "room temperature"), since comparatively large detecting signals can be obtained, they can not be accurately measured if the temperature of an object to be measured is nearly at room temperature, since only a small detecting signal ca be obtained.
It is necessary to increase the sensitivity of a thermopile itself in order to solve the above described disadvantage. A method, in which a sufficient temperature difference is produced between a heat sensitive portion and the standard portion by cooling or heating said heat sensitive portion by means of the separate cooling element or heating element, can be such a method of increasing the sensitivity of a thermopile (hereinafter referred to as "method of increasing the sensitivity"). However, this method inevitably requires a separate cooling or heating element and thereby requires a thermopile which is large-sized, complicated in construction and expensive.